TITLE: GCN CIRCULAR NUMBER: 35548 SUBJECT: IceCube-240105A: ZTF optical observation of blazar PKS 0446+11 DATE: 24/01/16 20:09:30 GMT FROM: Jannis Necker at DESY <jannis.necker@desy.de> Jannis Necker (DESY), Simeon Reusch (DESY), Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum) and Anna Franckowiak (DESY/Ruhr University Bochum) report: We observed the blazar PKS 0446+11 with the Palomar 48-inch telescope as part of our ZTF neutrino follow up campaign (Necker et. al, GCN 35510) of IceCube-240105A (Sommani et. al, GCN 35498). The blazar is detected over 2000 days with clear signs of variability. It recently reached its peak brightness in g-band in November after a around one month long rise in both g- and r-band, which coincides with activities in gamma-rays (ATEL #16398) and radio (ATEL #16399). At 2024-01-06T06:16:01.001280, we measured the all-time peak r-band brightness (17.1mag) only around 17 hours after the detection of IceCube-240105A, coinciding with the recent activitiy in X-rays (ATEL #16397). The blazar has since faded in both bands to 19.5mag in g-band and 18.3mag in r-band. The blazar was not selected as a candidate counterpart by our automatic follow-up pipeline because it got rejected as a star based on a metric derived from Pan-STARRS data (Tachibana & Miller, 2018, PASP 130 128001). ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/35548. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...